It is amongst the biggest and most renowned books on biographies. He summarized it from his book ‘The History of Islaam’.
The book is ordered according to the Hijri Calendar, beginning from the Sahaabah down to the end of the seventh century. The author did not include the biography of the Messenger - صلى الله عليه وسلم - or the four Caliphs and referred readers to ‘The History of Islaam’. However, the biography of the Messenger and the four Caliphs has now been included in the book by the publisher in the first two volumes.
He ordered the book according to Tabaqaat, it consists of about forty of them roughly following the method of books of Islaamic biographies.
The book is magnificent and very important, the author clarifies the full name of the individual, his lineage, his place of residence, his level of knowledge, his birth, his upbringing, his knowledge, his teachers, his students, the praise and criticism he/she has received along with mentioning the defects of the Ahadeeth he/she has narrated if any.